This invention relates to the electrolyte of an electrochromic display device, and more particularly, to the reform of the function by gelating the electrolyte.
In electrochromic display devices, usually an electrolyte solution has been used as the electrolyte. But when a solution is used, there have been problems such as the trapping of air bubbles or the destruction of the panel because of the difference in the rate of expansion between the panel and the liquid. To avoid these problems, use of a solid electrolyte has been considered, especially for the proton conductor, metal oxide thin films (e.g. silicon dioxide, tantalum oxide, etc). But these solid electrolytes have the defect of exhibiting a large electrical resistance. So that these devices exhibited a slow response required a large drive voltage. Furthermore, for these solid electrolytes the contacts between the electrochromic electrodes and the electrolytes, or between the counter electrodes and the electrolytes, have generally been considered as unreliable, i.e. in the case of a liquid, because of the fluidity of the liquid the contact could be expected to be enough, but, in the case of a solid, stripping could occur; especially when the external voltage has been applied for a long time, and this is an important factor affecting the device stability.
So far, the use of a gelated electrolyte solution has been tried, but, till now, these trials simply used an existing gelating reagent by mixing it with the electrolyte solution. As a result, the applied electric field was limited, and the technique could not be applied to arbitrary electrolyte solutions. Moreover the patterning of the electrolyte was difficult according to the prior art gelated electrolyte.